The life cycle of stars Flashcards
Describe the life cycle of a star (general)
For big stars: Protostar -> Main sequence -> Red Super Giant -> Supernova -> Neutron Star or Black Hole
For small stars (about the size of our sun): Protostar -> Main sequence -> Red Giant -> White Dwarf
How do stars initially form?
The form from clouds of dust and gas. The force of gravity makes the gas and dust spiral in together to form a protostar.
After a protostar has been formed… Gravitational energy is converted into [ ] energy so the [ ] rises. When the temp gets high enough, [ ] nuclei undergo nuclear [ ] to form [ ] nuclei and give out massive amounts of heat and [ ]. A star is born
Heat Temperature Hydrogen Fusion Helium Light
What could happen to the spare gas that isn’t used when a star is formed?
Smaller masses of gas and dust can pull together to make planets that orbit the star.
Describe the main sequence of a star. (3 main points)
Stars enter a long stable period, where the heat created by the nuclear fusion provides outward pressure to balance the force of gravity pulling everything inwards.
The star maintains its energy output for millions of years due to the massive amounts of hydrogen it consumes.
Main sequence several billion years
What causes stars to become Red (Super) Giants? Why are they red?
Eventually the hydrogen begins to run out. Heavier elements such as iron are made by the nuclear fusion of helium. The star the swells into a red giant (small star) or a red super giant (big star).
It becomes red because the surface cools
A small to medium sized star (after becoming a red giant) becomes [ ] and ejects its outer layer of [ ] as a [ ]. This leaves behind a…
unstable
dust and gas
planetary nebula
a hot dense solid core - White dwarf, which just cools down to a black dwarf and eventually disappears.
What happens after a big star has become a red super giant?
Start to glow brightly again as they undergo more fusion and expand and contract several times, forming elements as heavy as iron in various nuclear reactions.
Eventually they explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars.
What happens to the ‘star’ after a supernova?
The exploding supernova throws out layers of dust and gas into space, leaving a very dense core called a Neutron star. If the star is big enough this will become a black hole.
